A field experiment was made with chickpea (Cicer arietinum L.) at the Indian Agricultural Research Institute, New Delhi during the winters of 1984–5 and 1985–6 to study the effects of plant type and population density on growth and yield of chickpea. Cultivars BG 257, BG 261, BG 268 and BG 274 produced signficantly more grain with 1000 × 103 and 660 × 103 plants/ha, whereas the cultivar BG 209 produced the most at 500 × 103 plants/ha. Among the cultivars, BG 257 and BG 268 gave highest grain yield with 660 × 103 plants/ha.

Avalon winter wheat was grown in 1983 on a light-textured, sandy loam (Cottenham series) which had a subsoil pan with a maximum dry bulk density of 1·8 g/cm3 at 35 cm depth. This was destroyed on part of the site with a ‘Wye Double Digger’ so that crop growth in panned and pan-free soils could be compared. The interaction of the pan with soil water supply was studied by sheltering the crops during May, June and July and either withholding water completely or irrigating weekly back to field capacity.

The pan had a major effect on the vertical extension rate of the root system as monitored both by coring and from observation tubes. Roots were largely confined above the pan until March, but compensatory growth occurred within this soil layer and the total length of root was unaffected. At anthesis, roots had reached a maximum depth of 100 cm in the panned soil compared with 140 cm in the pan-free soil.

Early shoot growth and N content were substantially reduced by the pan because of the inaccessibility of mineral N in the subsoil. However, both the growth of the crop and N uptake recovered following top dressings of N fertilizer and, when water was not limiting, the pan had a negligible effect on grain yield.

Root and shoot growth were reduced by the fixed shelter, but the imposed drought did ot affect water use by the crops until after anthesis when the root systems were already fully developed. Without irrigation, the crop growing on the double-dug soil yielded 5% more than that growing on the panned soil, but there was no evidence for extra water use from the subsoil by the former crop. The best treatment (double-dug with irrigation) outyielded the worst (panned soil with drought) by 8%.

Effectiveness of the polyethylene glycol (PEG) test for measuring cell membrane stability (CMS) to select drought-tolerant genotypes in wheat was investigated. PEG test was compared with two other tests. Genetic variability of CMS was also investigated.

Drought was induced artificially in pot-grown plants and in excised leaves, and percentage injury in leaf tissues by drought stress as measured by CMS was compared with that by PEG test. Percentage injury in leaf tissues of pot-grown plants was not correlated significantly with that by PEG test. However, percentage injury in excised leaves was well correlated with that in PEG test. The results suggest that the PEG test has merit in measuring drought tolerance in wheat. Frequency distribution of CMS in winter wheat lines was closely related to the characteristic pattern of quantitative inheritance and therefore CMS of wheat seems to be controlled by polygene action.

Multiparous Corriedale ewes were maintained on a constant feed intake such that the body weight (i.e. live weight less gravid uterus) of single-bearing ewes at the end of gestation approximated their live weight at mating. The ewes were allocated to one of five groups, designated for slaughter at 0, 50, 90, 120 and 140 days of gestation. At slaughter, the gravid uterus was removed, weighed and its components dissected out and the contents of all sections of the gastro-intestinal tract were removed, weighed and sampled.

Foetal growth was described by a Gompertz model. It was predicted that, at day 150, a twin foetus would have been 0·95 of the weight of a single foetus but this difference was not statistically significant. The foetal proportion of the gravid uterus followed a sigmoid curve during gestation to reach a predicted value of 0·60 at day 150. Predicted birth weights represented 10·4 and 18·6% of maternal body weight in single- and twin-bearing ewes.

The digesta content of the rumen and of the whole gastro-intestinal tract was not significantly affected by gestation. However, there was a tendency for the values to decline to day 90, then increase during the last third of gestation. It was suggested that the decline was due to hormonal rather than direct physical effects. By contrast, the amounts of organic digesta constituents in the rumen descreased as gestation progressed (P < 0·01) indicating an effect of gestation on rumen propulsive activity.

To study the response of three sugarcane genotypes (CO 1148, COJ 64 and CO 1158) to variations in moisture availability in sandy loam soil (entisol), field trials were conductedat Lucknow (26·5° N, 80·5° E, 120 m altitude) during 1984–5 and 1985–6. Three moisture regimes, i.e. wet (irrigation at 75% available soil moisture (ASM)), moist (irrigation at 50% ASM) and dry (irrigation at 25% ASM) were maintained during the pre-monsoon (before June) period in spring-planted (February-March) sugarcane. During the summer months (until June)the variety CO 1148 had a significantly greater sheath moisture percentage than COJ 64 and CO 1158. Under stress conditions, leaf area index was reduced most in COJ 64 and least in CO 1148.Underground shoots and roots grew faster in CO 1148, and the growth of above-ground parts was quicker in COJ 64. Compared with the 75% ASM regime the reduction in cane yield in the 25% regime was more in COJ 64 and CO 1158 (31 t/ha) than in CO 1148 (12 t/ha). The water requirement of COJ 64 was greater than that of the other varieties. Therefore, for higheryields COJ 64 needed frequent irrigation whereas CO 1148 performed well even under moderate irrigation (50% ASM).

Faecal output of 287 beef cows consisting of Hereford (H × H), Simmental × Hereford (S × H), Friesian × Hereford (F × H) and Brahman × Hereford (B × H) breeding was estimated using controlled release of chromic oxide (Cr2O3). All cows were from 6 to 10 years of age and had grazed on one of three pasture systems in the subtropics of New South Wales since they were 7–8 months of age. These pastures were designated as being of high, medium and low nutritive value. Faecal organic matter output (FOMO) was estimated in each of four periods (early lactation, mid lactation, late lactation, and non-lactating) during one annual production cycle.

Herbage mass exceeded 2 t/ha on all pasture systems, but estimates of organic-matter digestibility, nitrogen content and pasture composition indicated large differences in pasture quality (high > medium > low). Live weight of cows averaged 604, 488 and 393 kg live weight on the high, medium and low pastures, respectively. There were significant differences in live weight between genotypes on the medium (B × H > F × H and H × H) and low (S × H ≡ F × H ≡ B × H > H × H) pastures but not on the high pasture).

FOMO and dry-matter intake (DMI) differed significantly between genotypes among lactating cows on all pasture systems. Rankings on high pastures were reasonably consistent in all periods: S × H ≡ F × H ≥ B × H ≥ H × H, as were those on low pastures, B × H ≥ S × H ≡ F × H ≥ H × H. Differences on medium pastures were significant only during mid-lactation when B × H ≡ S × H ≡ F × H > H × H. Significant differences between genotypes were observed among non-lactating cows on high pastures only, where H × H ≡ S × H ≡ F × H > B × H. Lactating females had significantly higher FOMO and DMI than non-lactating females when compared across genotypes during early lactation on all pastures.

A telemetry system based on calibrated radio transmitters implanted in the right sublumbar fossa of cattle is described. It was evaluated in different situations. Rectal temperature was used as a standard measure of body temperature. Implant temperatures were on average 0·2 °C higher than rectal temperatures. The magnitude of changes in the two temperatures in response to environmental stimuli were very similar but the implants changed faster in response to heat stress, feeding and exercise. When cattle were confined in unshaded yards the repeatability (within-animal correlation) of implant temperatures measured at different times of the day was 0·41 ± 0·05, compared with 0·30 ± 0·05 for rectal temperatures. It was concluded that there was less extraneous variation associated with telemetric measurement.

The telemetry system proved effective for monitoring the body temperature of grazing cattle within a range of 300 m. The repeatabilities of individual daily maximum and minimum temperatures were 0·43 ± 0·12 and 0·43 ± 0·11 respectively. Observations confirmed that cattle in part regulate their body temperatures by behaviours such as shading, grazing and exposure to wind. Thus body temperature whilst grazing was alone not a good index of physiological heat tolerance.

This paper re-analyses three experiments for which results have previously been published. A simpler model for aggression, based only on the proportions of the component yields of the mixed plots, is adopted. This greatly simplifies the analysis, which requires only a straightforward application of least squares, and gives much more accurate estimates of competitive power. Omission of some combinations from the mixtures included in an experiment presents little extra difficulty.

Various secondary matters, some of which have implications for the design of experiments of this type, are discussed in the paper. Graphical plots which throw light on the effect of sole yield differences on competitive power are exhibited. A logarithmic transformation of the data, often used to equalize the variance, was found to lead to underestimation of enhancement.

Dihaploids obtained from two tetraploids showed variation in tuber deformation resistance using a pendulum test and there were significant differences between them when used as parents in 2x × 4x crosses. Their ranking by tetraploid progeny means was the same as by clonal performance.

However, whereas the pendulum test was useful for the rapid measurement of rheological properties of tubers, there was found to be no correlation of control cultivar rankings using this test with those obtained using the squeezing test or farm survey data.

Dorset Horn and Corriedale ewes (breeds with low and high wool growing capabilities respectively) with single lambs were fed ad libitum on a pelleted roughage-concentrate diet. Following weaning at 6–7 weeks of age (live weight (LW) ca. 15 kg), ten entire male, ten female and ten castrate male lambs of each breed were housed in single pens and fed the same diet ad libitum. Body composition (fat, protein, water, ash and energy) was estimated from tritiated water space at 5 kg LW increments from 10 to 55 kg. Fleece weight was also estimated on each occasion.

The relationship between the weight of body components and fleece-free fasted live weight (W) for each sheep was described by a two-phase piecewise linear model, the slope in each phase representing the average composition of weight gain. In the first phase, the composition of weight gain did not differ between breeds and contained similar amounts of fat and protein (14%), 66% water and 5% ash. Within breeds females tended to be fattest. There were significant differences due to breed and sex in all body components in the second (fattening) phase. The fat content of gain was lower in Dorset Horn ewes and wethers (45 and 51% respectively) than in corresponding Corriedales (64 and 58%) with the males being even lower (44 and 41% respectively). Dorset Horns entered the fattening phase at a significantly higher W (26 kg) than Corriedales (23 kg), there being no sex difference within breeds. The combined effect of lower slope and higher weight at the commencement of the phase change in the Dorset Horns was to produce a considerable breed difference in fatness in the second phase of growth in ewes and wethers. Possible physiological reasons for the differences are discussed.

Gestational age-related changes in plasma free thyroxine (FT4) concentration in maternal and foetal goats were determined for 65–140 days of pregnancy. The placental permeability to maternal thyroxine (T4) and iodine (I) during the last trimester of pregnancy was evaluated.

The presence of T4 in foetal circulation at 65 days' gestation, the absence of a significant correlation between maternal and foetal levels and the absence of any transplacental diffusion of 125I–T4 showed autonomous foetal thyroid function during pregnancy in goats. Significantly low maternal FT4 was measured at 95 and 110 days' gestation (32·7 and 31·5 pmol/1 respectively). Plasma concentration increased to 48·6 pmol/1 at day 125 then fell before parturition to a level similar to that of non-pregnant goats (41·9 pmol/1). In contrast, foetal FT4 increased with gestational age to 110 and 125 days when levels of 64·0 and 59·1 pmol/1 respectively were greater than those at all other ages, suggesting that the foetal hypothalamic-pituitary-thyroid is functioning at a higher rate than the maternal system around this time. This was supported by increased foetal thyroid affinity for I when compared with the maternal thyroid at 110–140 days' gestation.

A significant cubic relationship between foetal FT4 and gestational age was established.

The tubers of Dioscorea composita Hemsl. contain a high level of diosgenin, and hence there is economic interest in this plant. Levels of diosgenin vary greatly in different clones of the species. Vegetative propagation was studied with a view to obtaining plants with high levels of diosgenin. In this study cuttings from 1-year-old vegetative plants were used for propagation. The cuttings were treated with a single application of indole-3-butyric acid (IBA) and several applications of 6 benzyladenine (6-BA). Rooting was never observed in untreated cuttings. Cuttings treated with IBA produced callus and roots. Early application of 6-BA delayed senescence but inhibited callus and root formation. New plants were obtained with one application of IBA followed by applications of 6-BA at 48 h intervals initiated 2 weeks after IBA application. In some experiments, all cuttings treated this way produced new plants.

Particulate fractions prepared from meadow hay, ranging in size from 0·1 to 2 mm, were incubated with rumen digesta from four cannulated Romney sheep fed the same hay. The rates of gas production, lipolysis of corn oil and hydrogenation of linoleic acid were measured.

The rate of gas production per g fermentable particles (FP) was approximately 30% lower with 1–2 mm than with the 0·1–0·4 mm particles. However, per m2 surface area the rate for the larger particles was found to be approximately 600% greater.

The rates of lipolysis of triacylglycerols and hydrogenation of linoleic acid were respectively 25 and 60% higher per g FP and 1100 and 1200% higher per m2 FP surface area with the 1–2 mm particulate fraction.

The same hay particulate fractions were incubated with pure cultures of Ruminococcus flavefaciens, since this organism is active in both lipid metabolism and cellulose fermentation. The rate of gas production and the number of organisms adhering to the particles were determined.

The effects of particle size on gas production were similar to those found when incubations were carried out with rumen digesta. Per g FP the rate was 40% lower with 1–2 mm than with 0·1–0·4 mm particles. However, per m2 surface area the rate was found to be approximately 450% greater with the former.

It was further found that although the density of the bacterial population on 1–2 mm particles was 600% higher than on the 0·1–0·4 mm particles, the rate of gas production per 109 bacteria remained unchanged.

We conclude that per m2 surface area fermentation, lipolysis and hydrogenation were more rapid with particles ranging from 1 to 2 than from 0·1 to 0·4 mm in size. This was due, at least in part, to microbial population density.

Digestibility trials were conducted at two stages of lactation with each of 107 Friesian cows using three diets (60:40, 75:25, 90:10 proportions of compound feed to medium quality hay fed long). Each cow received throughout lactation fixed daily allowances of one of these diets at either 2·26 or 2·63 times average maintenance requirements (MM), or was fed ad libitum, average intake equalling 3·07 MM. The digestibilities of the diets were also measured on immature cattle at 0·76 and 1·33 MM and sheep at 0·65 and 1·27 MM.

For all classes of stock the digestibility of dry matter increased linearly and that of fibre decreased curvilinearly with increasing proportion of compound in the diet. There was no interaction of effects of diet composition and amount consumed on digestibility of feed. The digestibility of both dietary components declined for the young cattle and sheep with increased intake. The digestibilities for lactating cows were lower than for other stock but did not change with amount consumed or milk yield. Digestibility was slightly higher for first and second calf cows than for adult cows; and was higher for organic matter in mid lactation compared with early lactation for adult cows.

These results for dairy cows conflict with the generally accepted interpretation that a linear decline in digestibility occurs from once to five times maintenance intake, embracing all classes of stock.

Three experiments which measured seed production and seed survival of annual medics (Medicago spp.) were conducted at Tel Hadya in north Syria. In Expts 1 and 2, conducted in consecutive years, the effects of rate and date of sowing on seed yield and its components were measured, while in Expt 3, the residual seed under summer grazing was monitored. In all three experiments seed permeability was observed at frequent intervals in summer and autumn. Selected ecotypes of three native medics (Medicago rigidula (L.) All., M. rotata Boiss. and M. noeana Boiss.) were compared with cultivars of M. truncatula Gaertn. and M. polymorpha (L.).

Seed production was greatest at sowing rates of 20–40 kg/ha. The native species produced more seed (up to 1000 kg/ha) than the cultivars (less than 500 kg/ha), although not significantly so in the case of the late-flowering ecotype of M. noeana. Seed yields of 500–1000 kg/ha were considered to be sufficient to perpetuate the pastures, but even higher seed yields are desirable.

Seed yield was closely related to number of pods in all ecotypes and, in Expt 2, up to 95% of flowers failed to produce mature pods. Flowers were more likely to mature at high sowing rate (256 kg/ha), in striking contrast to flower production itself which was greatest at sowing rates of less than 30 kg/ha. Flowers produced early in the season (before mid-April) were far more likely to give mature pods than late-produced flowers.

In late October, seeds of the native species were less permeable (10%) than those of the cultivars (30%), although their permeability was similar to that of the cultivars in Australia. In the three experiments the seasonal pattern of permeability varied, although there was a tendency for seeds to gain permeability in autumn. In Expt 1 there was a strong suggestion that the change from impermeability to permeability was reversible.

Ewes grazing mature pods gained weight, apparently as long as pod availability exceeded 10 kg/ha. It was clear that the condition of ewes was not a good guide to appropriate stocking rate for persistence of pastures, and that farmers will have to use other methods to assist them in grazing management.

Mean digestible energy (DE) intakes of 147 cows of three parities receiving three levels of DE including one ad libitum (about 2·2, 2·6 and 3·3 multiples of maintenance (MM)) drawn from three mixed diets containing hay and 60, 75 or 90% compound were calculated.

Rumen samples were taken from three-quarters of the cows at monthly intervals throughout the experiment. Molar proportions of volatile fatty acids (VFA) in the rumen were not affected by stage of lactation over the 36 weeks of the experiment. The proportion of acetic acid decreased and that of propionic acid increased with greater intakes and with higher proportions of compound in the diet. The proportion of n-butyric acid was little affected by level of intake but decreased with increasing proportions of compound. In young, non-lactating cattle given the same diets but at lower levels of intake, VFA proportions were unaffected by diet composition at intakes of about 0·7 MM but at intakes of about 1·3 MM the proportion of acetate decreased and that of propionate increased when the proportion of compound was increased from 75 to 90%.

The efficiency of milk energy production in relation to DE or metabolizable energy (ME) above maintenance decreased with increasing level of intake but was little affected by the proportion of compound. Partition towards live weight increased with level of intake in early lactation but not in late lactation. It also increased with higher proportions of compound in mid and late lactation but not in early lactation.

Estimates of the ME requirement for live-weight change (LWC) were in reasonable agreement with recently published standards in early lactation when live weight was decreasing, but later in lactation when live-weight gain was occurring, a much higher value was calculated which is difficult to reconcile with these standards.

Rumen VFA proportions were related to dietary fibre concentration and level of intake additively. The relationship to VFA proportions was close for milk fat concentration, but less so for energy partition towards live weight and none was apparent for the efficiency of ME utilization for milk energy production. It is suggested that both the reduction in milk fat concentration and the increase in milk yield in response to reductions in the fibre content of diets may be independently related to the increase in the proportion of propionate in the rumen VFA.

It is concluded that further progress in studies of the dietary factors affecting the efficiency of milk production will require measurements of nutrient uptake from the digestive tract and description of milk production and LWC in terms of their chemical composition rather than energy alone.

A trial to investigate possibilities of berry control by cultivation depth is described. Tubers planted at 10 cm produced significantly more potato plants in flower than those planted at 30 cm at the commencement of flowering. However, 3 weeks later the difference in numbers of flowers had disappeared. Emergence of overwintered tubers was about 53%, and of spring-planted tubers about 97%. Depth of planting did not affect emergence. A comparison of overwintered and spring-planted potato tubers showed earlier flowering and berry production by the overwintered tubers of about 1 week on average compared with the spring-planted tubers.

Six chemical treatments were compared at different concentrations and growth stages of potatoes and peas to assess potential control of berry production in potato volunteers growing in a vining pea crop.

Best control was found to be achieved with a combination of 4-(2-methyl-4-chlorophenoxy) butyric acid (MCPB) at 8300 mg a.i./l and Bentazone at 7300 mg a.i./l applied with the potato volunteers at full foliage to flowering stage, and before the pea crop reached the flowering bud stage, or by application of MCPB alone at 8300 mg a.i./l with the potato plants at full foliage to the pre-flowering stage. No chemical treatment either totally destroyed potato foliage, or completely suppressed potato flower and berry production, but it is argued that growers may reduce the effects considerably by careful observation and use of the appropriate chemical at the appropriate time.

Responses in live weight, milk production and calf growth to cobalt supplementation of groups of three and four pregnant heifers were measured to assess the value of serum vitamin B12 concentrations and the urinary concentrations of methylmalonic acid (MMA) and formiminoglutamic acid (FIGLU) for the detection of cobalt deficiency in cattle.

The administration of cobalt bullets to pregnant heifers, grazing pastures containing between 0·03 and 0·05 mg/kg cobalt, had no effect on either their live-weight change or milk production, or on the birth weight of their calves. MMA and FIGLU concentrations in the urine of unsupplemented heifers were low for the majority of the experimental period, although the concentrations of vitamin B12 in their serum (< 100 pg/ml) were in the range usually considered indicative of cobalt deficiency.

Calves from unsupplemented heifers had lower growth rates during the first 3 months of life and this was associated with intakes of 0·24–0·46 μg/day of vitamin B12 from milk, only 1–3% of those received by calves from supplemented heifers. Poor growth was associated with high urinary FIGLU concentrations, which increased from 500 to 2000 μmol/l between 1 and 3 months of age but decreased to less than 100 μmol/l between 3 and 4·5 months of age. Urinary FIGLU was a more reliable indicator of vitamin B12 deficiency in suckled calves than was urinary MMA, elevated levels of which were observed only at 3 months of age. The concentration of vitamin B12 in the serum of calves from unsupplemented heifers was consistently less than 100 pg/ml, but was not a reliable indicator of their functional vitamin B12 status, as judged by urinary concentrations of FIGLU and/or MMA.

The effect of inoculation with Azospirillum brasilense on growth, water status and yield of dryland sorghum (cv. RS 610 and cv. H-226) growing on stored soil moisture was examined in three field experiments conducted during the years 1983–5.

Plants were sampled at regular intervals, and the following characteristics were measured: dry-matter accumulation, leaf area, grain yield, percentage nitrogen and phosphorus in leaves, leaf water potential, canopy temperature, transpiration, stomatal conductance and soil water depletion.

Inoculation led to an average increase of 19% in total stover dry-matter yield, as a result of higher rates of dry-matter accumulation during the early stages of growth. Azospirillum inoculation caused a 15–18% increase in grain yield in all three experiments. This increase was associated with a greater number of seeds per panicle.

The water regime of sorghum plants was improved by inoculation, as seen in their higher leaf water potential, lower canopy temperatures and greater stomatal conductance and transpiration. Total extraction of soil moisture by inoculated plants was greater (by about 15%) and occurred from deeper soil layers, compared with non-inoculated controls.

These findings indicate that inoculation with Azospirillum can lead to yield increases in dryland grain sorghum, primarily through improved utilization of soil moisture.

In intermediate deepwater conditions (15–50 cm), direct seeding was superior to transplanting in 20 cm of water. Varieties with greater plant height performed better under transplanted conditions. Nitrogen fertilizer application at 40 kg/ha increased the grain yield under both direct-seeded and transplanted conditions. Though yield of the transplanted crop was less than that of the direct-seeded crop, the decrease was less in the crop given nitrogen fertilizer.